Path: utzoo!utgpu!water!watmath!clyde!att!pacbell!ames!claris!apple!dan
From: dan@Apple.COM (Dan Allen)
Newsgroups: comp.sys.mac.programmer
Subject: Re: System 6.0 and 2nd screen
Message-ID: <14441@apple.Apple.COM>
Date: 21 Jul 88 23:30:45 GMT
References: <3316@polya.Stanford.EDU>
Reply-To: dan@apple.apple.com.UUCP (Dan Allen)
Organization: Apple Computer Inc, Cupertino, CA
Lines: 22

In article <3316@polya.Stanford.EDU> rwilson@polya.Stanford.EDU (Randy Wilson) writes:
>I have been writing a Mac video game for some time, and just got around to
>testing it on system 6.0.  When it starts writing to the 2nd graphics screen,
>it crashes, id=02.  It turns out that BufPtr is in the middle of the 2nd
>screen, so I assume I am trashing info in high memory; it worked on all 
>previous systems.  Further, the launch call to allocate the 2nd succeeds, and
>
>Does anyone know what Apple has put in high memory?  Have they finally made
>good on their threat to mangle programs that use the 2nd screen?  If so, why

This is not a definitive answer, but I believe the problem is related to
the Sound Manager.  System 6.0 is the first system to backpatch the SM
to the Mac Plus and SE.  I recall some conflict between sound and the
2nd screen.  The Mac II has never supported a 2nd screen, due in part to
its having the screen memory located out on a video card and not part of
normal user RAM.

Perhaps someone else can confirm this hunch.

Dan Allen
Software Explorer
Apple Computer